| 英文摘要 |
Visibility is related to air quality, but it is not equivalent to air quality. Atmospheric visibility can be analyzed by objectively measuring the atmospheric extinction coefficient. The atmospheric visibility is related to absorbing and scattering light by aerosol particles, which depends on PM’s physical and chemical properties and vary significantly in space and time. It is mainly affected by the chemical composition and particle size of suspended particles in the air, and it is important to explore the relationship between these physicochemical parameters and their influences on light extinction. Therefore, it requires long-term, high-resolution monitoring and analysis and analysis of visibility changes. All the above would enable us to understand aerosol’s impact on atmospheric visibility and mitigate the impairment. The project aims to explore the factors governing atmospheric visibility, investigate the major pollution sources of degrading visibility, study the causes of the development of events, and formulate mitigation strategies. Both manual filter sampling and real-time monitoring were conducted at Tunghai and Zhongming stations for six seasons. The results showed that visibility in the Taichung area was largely affected by PM mass concentration, aerosol chemical composition, and particle size distributions. Winter was found to be the season with the highest average value of particle extinction coefficient and frequently having low-visibility days. By comparing clean and episode days, it is found that the contribution of NO3- in aerosol particles increased significantly during the episodes, which might be associated with high precursor levels as well as a high atmospheric oxidation capacity. In addition, the low ventilation coefficient (the product of wind speed and boundary layer height) is the key parameter for activating the visibility impairment. Lastly, we have successfully applied the positive matrix factorization (PMF) on particle chemical composition and particle number size distribution to reveal the potential pollution sources. The results were used to evaluate and formulate mitigation strategies. This report also includes the economic benefit analysis for conducting this whole project.
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